1. Field of the Invention
The present invention relates to a method for manufacturing a wiring and a method for manufacturing a semiconductor device such as a light emitting device or a liquid crystal display device by a droplet discharge (ink-jet) method utilizing a photocatalytic reaction. In addition, the invention relates to a droplet discharge apparatus for forming them.
2. Related Art
A droplet discharge technique typified by a piezo method or a thermal jet method, or a continuous droplet discharge technique has attracted attention. This droplet discharge technique has been used in printing a type and drawing an image. However, an attempt to apply it to a semiconductor field, for example, micropattern formation or the like has begun in recent years.
On the other hand, there is a method for forming a patterned metal film made of only an absorption metal atom by soaking a base material provided with a substance having a photocatalytic function over its surface in a metal-ion-containing aqueous solution including alcohol, by drawing on the base material with a predetermined pattern by laser light, and by soaking the base material in an aqueous solution capable of forming a complex to remove the absorption metal ion, as a conventional method for forming a metal wiring by a photocatalytic reaction (for example, Reference 1: Japanese Patent Laid-Open No. 9-260808).
In addition, titanium oxide (TiO2) used as a photocatalytic material is an N-type semiconductor. It is known that a photocatalytic reaction is caused on its surface when the surface is irradiated with light of a wavelength in an ultraviolet region and it has an effect such as deodorization, mildew proofing, antifouling, or antibacterial due to activated species generated on the surface. There are three types of titanium oxide called a rutile type, an anatase type, a brookite type, each of which has a different crystal structure. It is the anatase type that has the highest photocatalytic activity among them.
In the case of forming a wiring by using an ink-jet method as described above, a droplet (a dot) discharged from an ink-jet nozzle spreads on a wiring formation surface, and it is difficult to narrow a line width (simply referred to as a width) of a wiring. On the other hand, as a semiconductor device, specifically, a pixel portion included in a semiconductor device is made to have higher precision and higher aperture ratio, it is required to form a narrower wiring.
Further, in the case where the wiring formation surface is liquid-repellent, a landed dot easily rolls on the surface and coheres. Therefore, it is difficult to draw a continuous line in a desired region.
Thus, it is difficult to form a small wiring in width and to control a position of a wiring to be formed in a designated position by an ink-jet method.